Uncontrolled surface and underground coal fires burn in over 15 countries around the world, including Australia, South Africa, and the United States (the fire beneath the town of Centralia, Pennsylvania is one of the better-known examples of this phenomenon). They are a particular problem in China, where they consume an estimated 15 to 20 million tonnes of coal per year.¹

The occurrence of uncontrolled coal fires long predates industrial coal mining, and some still begin naturally. However, mining is the most important cause of coal fires today.^{2 3} By exposing coal to air, mining activities allow oxidation to take place, encouraging the spontaneous combustion that often causes the fires.⁴ In China, small coal mines operating without effective safety standards and precautions are especially problematic, and fires can also result from abandoned mines that have not been adequately sealed off.⁵

The relative obscurity of mining-induced coal fires belies their potentially severe environmental impacts. Uncontrolled coal fires emit large quantities of greenhouse gases, including carbon dioxide, methane, and nitrous oxide.⁶ It has been estimated that emissions from Chinese coal fires alone represent 0.1-0.3 per cent of all human-induced carbon dioxide emissions⁷ – yet, due to uncertainty surrounding the prevalence of these fires and their impacts, their emissions are generally not accounted for in climate modeling exercises.⁸

Beyond their climate impacts, uncontrolled coal fires contribute to methyl mercury build-up in global fish stocks and, ultimately, in humans.⁹ Air pollution from coal fires damages plant life¹⁰ and harms human health, causing increased rates of lung cancer and other respiratory diseases among people living nearby.¹¹ Consumption of coal by underground fires can lead to the opening of dangerous cracks in the earth. In China, coal fires are also a significant cause of fatal coal mining accidents.¹²

Research is ongoing to better locate, map, and control coal fires. While environmental impacts are frequently noted as a concern, another motivation is the desire to access coal deposits that are either in danger of being consumed by the fires or rendered unmineable by their proximity to them. ^{13 14}

While eliminating coal fires brought on or exacerbated by mining is a worthy goal, it is somewhat undermined when the intent is further coal extraction and combustion, which carries its own significant environmental costs. Rather than being considered an impediment to coal use, uncontrolled coal fires should be viewed as an additional danger associated with continued reliance on this resource – one that remains long after mining projects have ended and attention has turned elsewhere.